Photoconductor-carrying drum assembly

ABSTRACT

A photoconductor-carrying drum assembly is provided comprising a plurality of frame structures each with a pair of pivotal support members which normally mate together to define a curved surface with a flexible photoconductor element resting thereon. The support members of each frame structure swing inwardly when the structure reaches a predetermined angular position upon rotation of the drum assembly, whereby the photoconductor element assumes a substantially planar configuration for exposure. Each photoconductor element extends between supply and take-up spools carried by the frame structure together with a mechanism for periodically advancing the photoconductor in the imaging area.

United States Patent 1 [191 Kolib'as [451 July 30, 1974PHOTOCONDUCTOR-CARRYING DRUM ASSEMBLY [75] Inventor: James AndrewKolibas, Broadview Heights, Ohio [73] Assignee: Addressograph-MultigraphCorporation, Cleveland, Ohio 221 Filed: Dec.3,1973

121] Appl. No.: 421,258

[52] US. Cl 355/3 R, 355/16, 101/132 [51] Int. CL; G03g 15/00 [58] Fieldof Search 355/3 R, 3 DD, 16; 96/1 PC; 101/132 [56] References CitedUNITED STATES PATENTS 3,563,734 8/1967 Shely '355/16 UX 3,584,947 6/1971Mihalik 355/16 3,706,489 12/1972 Moxness et al. 355/3 R OTHERPUBLICATIONS IBM Technical Disclosure Bulletin, Vol. 15, No. 4,

September 1972, Xerographic Drum, Berlier et al.

Primary Examiner-Robert P. Greiner Attorney, Agent, or Firm-Harry M.Fleck, Jr.

[57] ABSTRACT A photoconductor-carrying drum assembly is providedcomprising a plurality of frame structures each with a pair of pivotalsupport members which normally mate together to define a curved surfacewith a flexible photoconductor element resting thereon. The supportmembersof each frame structure swing inwardly when the structure reachesa predetermined angular position upon rotation of the drum assembly,whereby the photoconductor element assumes a substantially planarconfiguration for exposure. Each photoconductor element extends betweensupply and take-up spools carried by the frame structure together with amechanism for periodically advancing the photoconductor in the imagingarea.

32 Claims, 13 Drawing Figures PATENTEDJULIiOIHH SHEU 1 0F 6 III III/I]PATENTEI] JUL 3 01974 SHEET 5 BF 6 PHOTOCONDUCTOR-CARRYING DRUM ASSEMBLYBACKGROUND OF THE INVENTION The present invention'is generally relatedto electrophotography and, more particularly, to a drum assembly for usewith an electrophotographic reproduction apparatus and which carries anadvanceable web of flexible photoconductor and includes means forflattening the photoconductor during exposure.

In recent years, various types of electrophotographic reproductionmachines have been proposed or manufactured which utilize the well knownprinciples of photoconductivity. Various plain paper'type copiers havebeen provided which include drums with cylindrical photoconductivesurfaces, such as selenium, which are exposed to the image of theoriginal document to be copied to provide a latent image pattern.Typically, pattern is developed by the electrostatic application oftoner particles'which are ultimately transferred and fused to a plainpaper copy. The use of a cylindrical drum with a photoconductive surfacehas the advantage of ease of disposition of the various process stationsaround the circumference of the drum. However, such drum structures areexpensive to manufacture or replace, as is occasionally necessary.Furthermore, since the photoconductor surfaces are not flat, it isnecessaryto expose such progressively by line scanning the originaldocument. Whatever means of scanning is employed, it necessarilycontributes substantially to the cost of manufacture of the apparatusand significantly reduces the copy production rate. v

In an attempt to increase the copy production rate, several plain papercopiers have been proposed which employ a flash exposure of the originalonto a flat photoconductor surface, rather than a curvedsurface asprovided with the earlier drum structures. One such proposed systemincludes an endless photoconductor belt or web, a portion of whichassumes a planar configuration to accommodate imaging at a flashexposure statiomSubsequent to exposure, the photoconductor web is,advanced past the various process'station's to ultimately produce aplain paper copy. Typically, the photoconductor web is of sufficientlength to accommodate several image areas, whereby several copyprocesses may be carried out simultaneiou sly to further enhance thecopy production rate. However, such endless belt arrangements requirethat the belt pass along a rather tortuous path in order to hold thesize of the machine within reasonable dimensions. This subjects the beltto undesirable flexing and bending along its path around rollers ofrelatively small radious, which could eventually weaken thephotoconductor support material to the point of breakage and possiblycause deterioration of the organic or inorganic photoconductor surface,necessitating replacement of the belt. Another problem is that theknownphotoconductor surfaces which are more suitable for withstandingthe flexing have relatively short life spans in that they becomefatigued within a relatively small number of copy cycles, thus requiringperiodic replacement of the belt if quality copies are to be produced.

In attempts to overcome the above-mentioned problems presented by theendlessphotoconductor belt arrangement, various mechanical drumstructures have been proposed which periodically flatten thephotoconductor element for flash exposure. One such arrangement isdisclosed by US. Pat. No. 3,584,947 to N. Mihalik and includes acylindrical drum which carries several photoconductor plates around itscircumference, each plate defining an image area. The plates arenormally held in a curved configuration, but are periodically unwrappedfrom the drum surface to provide a planar configuration during exposure.Each plate is clamped, or otherwise held, along its oppositeedges by apair of lever mechanisms which are caused to move outwardly beyond thedrums circumference to flatten the associated photoconductor plate whenthe plate is positioned for exposure. Since each photoconductor plateperiodically assumes a planar configuration, flash type exposure may beutilized, thereby providing relatively high speed copying. On the otherhand, however, the mechanisms which effect unwrapping of the plates eachinclude a considerable number of moving parts which are costly tomanufacture and tend to decrease the overall liability of the machine.Also, since the levers move outwardly, considerable clearance must beprovide around the drum making it necessary to increase the size of themachine and sacrifice compactness. Most important, is the fact that thephotoconductor plates are susceptible to film build-ups and/ordeterioration after'a number of copy cycles, necessitating frequentservicing or replacement of the photoconductor plates, thus increasingthe effective cost of operation.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a novel photoconductor-carrying drumassembly for use with anelectrophotographic reproduction apparatus to provide the advantages ofhigh speed copying and at the same time provide reliable operationrequiring a minimum amount of servicing.

Another object of the present invention is to provide a versatilephotoconductor-carrying drum assembly which is capable of periodicallyproviding a portion of flattened photoconductor for flash exposure, yetis of relatively simple, highlyreliable construction which is economicalto manufacture and maintain.

It is a further object of the present invention to provide a unique drumassembly comprised of a plurality of frame structures, each carrying aphotoconductor web extending between a supply spool and a take-up spool,whereby the web may be conveniently advanced a predetermined amount toreplenish a fatigued or damaged portion of the photoconductor.

Still another object of the present invention is to provide a compactdrum assembly comprising a pivotal support structure defining a normallycurved support surface for a flexible photoconductor, the supportstructure being periodically pivoted inward toward the axis of drumrotation, whereby the photoconductor assumes a planar configuration forflash exposure.

Yet a further object of the present invention is to provide aphotoconductor-carrying drum assembly includ ing a pair of support doorswhich are folded inwardly in response to rotation of the drum assemblyto a predetermined angular position, thereby presenting a flattenedphotoconductor element to a flash exposure station.

It is a further object of the present invention to provide a versatiledrum assembly carrying at least one photoconductor web and includingmeans for advancing the web a predetermined amount upon completion of apredetermined number of copy cycles.

Still another object of the-present invention is to provide a uniquephotoconductor-carrying drum assembly including a mechanismfor'incrementally advancing or creeping the photoconductor element toincrementally remove fatigued portions of the photoconductor from theimage area, each advancement occurring after a predetermined number ofcopycycles.

Additional advantages of thisinvention will become apparent from thedescription which follows, taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS tions shown in section and with one ofthe frame structures in a folded position to conductor element;

FIG. 4 is a partial plan view of thedrum assembly takenalong section 44of FIG. 3; 4

FIG. 5 is a partial end view of the drum assembl showing the associated.cam plates;

FIG. 6 is an exploded perspective view of a first embodiment of thephotoconductoradvance mechanism associated with the drum assembly;

FIG. 7 is a sectional view of the photoconductor advance mechanismillustrated in FIG. 6;

FIG. Sis a simplified end-view of the drum assembly as utilizing theadvance mechanism shown in FIG. 6 together with an arcuate actuationmember;

FIG. 9 is a partial side elevation of the drum assembly and actuatorillustrated in FIG. 8;

FIG. 10 is an end view of a single frame structure of the drum assemblyprovided with a second embodi ment of the advance mechanism;

FIG. 11 is an exploded perspective view of the frame structure andadvance mechanism illustrated in FIG.

FIG. 12 is a side elevation of the mechanical counter and advanceratchet illustrated in FIG. 11, with secprovide a flattened phototionsremoved;

FIG. 13 is a sectional view of the tensioning mechanism associated withthe supply spool shown in FIG. 11

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now, moreparticularly, to FIG. 1 of the drawings, a typical electrophotographicreproduction apparatus is generally indicated by the numeral andincludes a rotatably supported drum assembly 22 mounted in a housing 24.The drum assemblyis operatively connected to a drive motor, notillustrated, which effects controlled rotation of the drum'assembly in aclockwise direction as indicated by arrow 26. The drum assembly iscomprised of four quadrants or sections 28, 30, 32 and 34, each of whichcarries its own photoconductor element which defines a correspondingimage area, as hereinafter explained.

Disposed-about the periphery of the drum assembly 22 are a number ofprocessing stations which carry out the conventional steps of thexerographic copying process. An' initial charging station may ,bedefinedby a conventional corona discharge unit 36, or equivalent device, whichprovides a uniform charge onthe surface of the photoconductor elementprior toexposure. A flash exposure station, generally indicated by thenumber 38, is provided with a pair of flash lamps 40, preferably of thexenon type, which irradiates a document 42 resting upon a transparentwindow 44 in face-down orientation; This provides an image of light andshadow which is projected by a stationary lens 46 onto an image plane48, which coinsides with the photoconductor element which is of a planarconfiguration during exposure.

The next station in the direction of rotation'of drum assembly 22 isadeveloper unit 50, of a conventional type, which applies tonerparticles to the latent image pattern on the associated photoconductorelement to define a developed image. Subsequent to development,

and the toner image is fused to the copy sheet at a fusing station 56.The finished copy is then transported by appropriate means, notillustrated, to a output hopper,

- such as that indicated at 58. Various transfer and fusing techniquesare well known to those skilled in the art of electrophotography, and adetailed description'of such is.deemed unnecessary for the purposes ofthis specification.

Since some residual toner remains on the photoconductor element, it isnecessary to clean the element prior to re-exposure. Typically, this isachieved by' a cleaning station including a pre-clean'corona unit 60which losens the remaining toner particles, and a cleaning unit 62whichbrushes the toner particles from the surface of the photoconductorelement.

It will be appreciated that the drum, assembly of the present inventionprovides a plurality of image areas spaced around its circumference,whereby the various process stations may be operated concurrently toprovide a high copy production rate. For example, when making multiplecopies, the exposure operation can be carried out at quadrant 28 whilethe development operation is taking place at quadrant 30, together withthe transfer and cleaning operations at quadrants 32 and 34,respectively. Since exposure is achieved by a flash, rather thanscanning, the drum may be rotated at a high rate of speed whichsignificantly enhances the copy production rate of theimachine.

. Referring now to FIG.-2 of the drawings, the preferred embodiment ofthe drum assembly'may be seen in more detail. Each quadrant or sectionof thedrum assembly is defined by an independent framestructure thatthey define a curved support surface for a flexible photoconductorelement 78. Preferably, photoconduc-' torelement 78 is in the form of anelongated web extendingbetween a supply location and a take-up locationin the associated frame structure and includes a layer of organicphotoconductor, such as polyvinyl benzocarbazole, on a base ofalluminized Mylar of approximately 3 to 5 mils thickness. The portion ofthe photoconductor element which overlies support members 64 and 66defines an image area which is normally of curved, part-cylindricalconfiguration. During the flash exposure operation support members 64and 66 are moved inwardly, whereby the photoconductor element assumes asubstantially planar configuration, as hereinafter explained.

Each of the frame structures is mounted to a common hub 92 which isprovided witha pair of dovetails 94 and a group. of key fins 96 whichcooperate with key ways 98 and 100m end plates 68 and 70. This providesconvenient installation and removal of each frame structure from the hubpermitting each frame structure to be removed independently 'of theothers. Each frame structure may be secured in place against axialmovement by a stop member 102 and lock tab 104, or other appropriatefastening means.

Preferably, the movement of the support members of each frame structureis achieved by way of cam followers 80 and 82 which are disposedoutboard of end plate 68 and are carried by mounting pins 84 and 86 associated with support members 64 and 66, respectively. The mounting pinsextend through appropriate slots 88 and 90 formedin the end plate.

With reference to FIGS. 3-5, the operation of each frame structure maybe more clearly understood. As mentioned above, the support members arenormally disposed in their outer positions, whereby they mate togetherto define the curved support surface for the photoconductor element.Preferably, each frame structure is provided with a pair of leaf-springmembers 106 and 104 mounted to end plate 68 with movable end portionswhich retentively' engage mountingpins 84 and 86 to normally retain thesupport members in their outer positions. Each of the cam followers 80and 82 travel in circular path with the drum assembly until it engages acam surfaceassociated with a group of cam plates .110, 112, 114 and1.16, illustrated in FIG. 4 and 5. The cam plates are effective toovercome the retaining forces of leaf-springs 106 and 108, allowingsupport members 64 and 66 to move inwardly toward the axis of drumrotation to a collapsed or folded position as illustrated in theuppermost quadrant of FIG. 3. lnward movement of the support members isaccompanied by a corresponding disengagement from the intermediateportion of the photoconductor web 78, permitting it to assume asubstantially planar configuration for flash exposure. Since the lengthof the intermediate portion of the photoconductor web is somewhat lesswhen in the planar configuration than when in the curved configuration,appropriate tensioning means are provided for pulling the web tautduring collapse of the support doors. Typical embodiments of thetensioning mechanism are hereinafter described.

With particular reference to H0. 5, the arrangement of the cam surfaceswhich effect movementof the support members may be seen in more detail.Cam plates 110, 112, 114 and 116 are shown in solid line, while portionsof the drum assembly being shown in phantom for the sake of clarity. Thesurfaces associated with the cam plates define a pair of distinct pathsfor followers and 82 to appropriately time the opening and closing ofsupport members 64 and 66 such that the photoconductor element assumes aplanar configuration when the drum assembly is at a predeterminedangular position corresponding to the exposure operation. In addition,the cam surfaces carefully control the movement of the doors relative toeach other to assure clean engagement and disengagement therebetween.

- It will be appreciated that as the drum assembly is rotated in aclockwise direction, as illustrated in FIG. 5, cam followers 80 and 82enter the cam paths at an area generally indicated by the numeral 118.The folding operation is initiated by engagement of follower 80 withcam'surface 120 defined by plate and axially spaced from a correspondingcam surface 122 associated with cam plate 112. Since follower 80 engagesthe cam plate prior to follower 82, it may be referred to as the leadingcam follower, with the corresponding cam surfaces being referred to asthe leading? cam surfaces. Similarly, follower 82 is herein referred toas the trailing cam follower, and the corresponding cam surfaces arereferred to as the trailing cam surfaces.

Leading cam surface curves radially inward toward the axis of drumrotation, whereby it is effective to influence leading follower80radially inward sufficiently to overcome the retaining forces ofleaf-spring 106. Subsequent to release from leaf-spring, support member66 continues to pivot inwardly under the influence of gravity withfollower 80 riding along cam surface 124. The leading cam surface curvesradially outward at a point indicated at 126 and is effective toinfluence follower 80 outwardly to return of support member 66 to itsoriginal position subsequent to exposure. Returned to the originalposition occurs when follower 80 reaches theapex of the leading camsurface as indicated at 128. At this position, leaf-spring 106 iseffective to retain support member 66 in its outermost position duringthe development, transfer, and cleaning operations explained above. v

Shortly after follower 80 initiates inward movement of support member 66trailing follower 82 engages the trailing cam surface at 122 to initiateinward movement of trailing support member 64. As mentioned above,follower 82 is axially spaced from cam follower 80 and follows a pathwhich is separate from the leading cam path. Plates 112 and 116 providea pair of parallel cam surfaces, generally indicated by the 'numerals130 and 132, which define the trailing path. Cam surface 132 is shapedto prevent trailing support member 64 from striking member 66 duringeach cycle for exposure. After exposure, the trailing cam surfacesinfluence follower 82 outward to return support member 64 to itsoriginal position in engagement wiht support member 66. It will beappreciated that the cam surfaces accurately control movement of thesupport members of each frame structure as the drum assembly is rotated.Of course, it is not intended that the present invention be limited tothe cam configurations illustrated in H0. 5 as various types ofappropriate cams may be utilized, if desired. i

With reference to FlGS. 6 and 7, a first embodiment of thephotoconductor advance mechanism of the drum assembly is illustrated.Preferably, this mechanism is intended for advancing the photoconductortermined number of copy cycles. However, it will be appreciated that themechanism may be readily adapted for advancing the photoconductor alessor or greater distancethan a single image area. The photoconductorweb extends from a supply spool 134, through a pair of supply controlrollers 136 and 138, over the support members 64 and 68, between take-upcontrol rollers 140 and 142, to a take-up spool 144. Advance of the webis effected by controlled rotation of.roller 142. Also, coller 142serves to provide the appropriate tension'ing of the web when thesupport members are folded inwardly during exposure, whereby theintermediate portion of the web assumes a substantially planarconfiguration. This tensioning is provided by a coil spring 146 with itsinner end 148 affixed to shaft 150 by way of aslot 152, or otherappropriate fastening means. Roller 142 is affixed to shaft 150 forrotation therewith, together with a gear 154 in meshing engagement withgear 156 associated with roller 140. Both rollerj140and gear 156 arerotatably mounted to a supexposure the excess intermediate portion ofthe web is taken up by spring 146 which rotates roller 142 in aclockwise direction. This maintains tension on the'web to assure thatsuch is in a planar configuration at the exposure station. When thesupport members are moved outwardly subsequent to exposure, tension onthe web overcomes the forces of spring 146, whereby a length of the webis pulled back through rollers 142 and 140, permitting'the web to assumeits original curved configuration.;

Y During cycling of the support members, the photoconductor web isprevented from creepingforward due 8 spring is fixed to a toothed drivepulley 174 for rotation therewith. A toothed belt 176 driving lyconnectspulley 174 with a toothed advance pulley 178. Drive pulley 174is rotatably mounted to the end of shaft 150 and is provided with a pin180 which engages a corresponding finger 182, associated with shaft 150,when the spring is fully wound. Since the inner end 148 of the coilspring is affixed to shaft 150 and the outer end 172 is affixed to drivepulley 174, rotation of the'drive pulley independent of shaft 150 iseffective to wind the spring. After pulley 174 has been advanced apredetermined amount in a clockwise direction, pin- 180 engages fingers182 causing the drive pulley' and shaft 150 to rotate in unison in aclockwise direction. This occurs during advance of the photoconductor,as hereinafter explained. a

As mentioned above, the winding operation is initiated by the cycling ofsupport membersssupport member 66 is provided with a lever arm 184 whichcarries a pin 186 extending between the legs of a bifurcated member188,. A nylon bushing 190 is mountedto a shaft 192 and carries member188 in frictional engagement under the influence of adjustable clampbolt 1,94. Shaft 192 is supported by a one-way bearing 1 96, of aconventional type, which permits rotation of the shaft in a clockwisedirection only. Shaft 192 is provided with a hollow or bore which isfrictionally engaged by an expandable nylon shaft 198, as indicated at200 in FIG. 7. This frictional engagement may be adjusted by a screw 202which is threaded into shaft 198 such that tightening of the screwcauses the shaft to expand outwardly to increase its frictionalengagement with the interior of shaft 192. Shaft 198 is also providedwith a pair of drive fingers 204 which operatively engage appropriatekey ways 206 formed in take-up spool 144.

The spring winding operation may be described as follows. When thesupport members are folded inwardly for an exposure operation,bifurcated member 188 is rotated slightly counterclockwise. Thismovement is lost motion, as one-way bearing 196 prevents hollow shaft192 from rotating in a counterclockwise direction. As the doors arereturned totheir original to thepinching action of supply controlrollers 136 and to bring a friction washer 168 in snug engagement withthe end of roller 136 under the influence of a spring washer. 170. Theclamp nut 166 is adjusted to provide sufficient drag to prevent creepingof the photoconductor, yet allow advancement of the photoconductor undercontrol of the advance mechanism, as hereinafter explained.

In order that the intermediate portion of the web is held taut duringeach exposure itis essential that spring 146 be sufficiently wound toeffect take up of the excess when the doors are swung inwardly. This isachieved by winding the spring each time thesupport doors, are cycled.An outer end portion 172 of the coil position, member 188 is rotatedslightly in a clockwise direction. Normally, this motion is transmittedto shaft 192, which in turn causes rotation of advance. pulley 178 anddrive pulley 174 through belt 176. Thismovement winds the coil spring146 in a clockwise direction. Each operation of the support door windsthe spring slightly until pin engages finger 182, at which time thespring is fully wound. Cycling of the doors subsequent to full windingof the spring causes bifurcated member 188 to slip on nylon bushing inboth the clockwise and counterclockwise directions.

It will be appreciated that clockwise advancement of 174 is rotated in aclockwise direction, causing corresponding'rotation of shaft 150 androller 142. Rollers 140 and 142 rotate in unison through gears 154 and156 to take up the desired length of photoconductor web. At the sametime, pulley 178 is driven to rotate take-up spool 144 clockwise by wayof shaft 198. Typically, the photoconductor web is advanced an entireimage area after a predetermined number of copy cycles. When the advanceoperation has been completed, coil spring 146 is left in a fully woundcondition, such that it is capable of pulling in the excess photoconductor onthe first cycle of the support doors.

It will be appreciated that operation of the advance mechanismillustrated in FIGS. 6 and 7 may be effected in various manners. FIGS. 8and 9 disclose a typical arrangement for effecting advancement of thephotoconductor through rotation of drive pulley 174. An arcuateactuation member 208 is supported by appropriate means, not illustrated,and is operatively connected to a solenoid 210. A control circuitassociated with the copy machine is connected to solenoid 210 byway ofleads 212 for energization of the solenoid, for example, after apredetermined number of copy cycles. Of course, the control circuit mayinclude means for otherwiseenergizing the solenoid, such as an Advancepush button to effect manual advancement in the event of damage orexcessive wear to the photoconductor.

Actuation member 208 is provided with a plurality of gear teeth 214arcuately disposed on the lower side of the actuation member todefine anarcuate rack. Drive pulley 174 is considerably wider than belt 176 toprovide an exposed portion 216, illustrated in FIG. 9, which underliesactuation member 208. The actuation member is normally disposed in aposition shown in solid line in FIG. 8. When solenoid 210-is energized,the actuationmember is moved downward to a position shown inphantom inFIG. 8 at 208a. In thisposition, rack teeth 214 drivingly engage theteeth of drive pulley 174. With the drum assembly rotatingin acounterclockwise direction, drive pulley 174 is driven in a clockwisedirection. This operation effects advancement of the photoconductor,with the amount of advancement being determined by the length of thearcuate rack. The solenoid maybe energized for an'entire revolution ofthe drum assembly, whereby all :four of the photoconductor webs areadvanced in a single operation. On the otherhand, if desired,.thesolenoid energization may be only mementary, whereby a single quadrantphotoconductor is advanced. It will be appreciated that thephotoconductor advance arrangement illustrated in FIGS. 8 and 9 is notlimited to the actuation member being mounted directly above the drumvassembly. lt may be more suitable to mount the actuation member to oneside or the other, or beneath the drum assembly, such that advancementoccurs while the photoconductor is in the curved configuration.

Referring now, more particularly, to FIGS. 10 and 10 direction to takeup any slack photoconductor which has been advanced by rollers 222 and224.

A drive ratchet 228 which is keyed or otherwise affixed to the driveshaft 220 to effect rotation thereof by way of a drive pawl 230 afterthe counter completes the preselected number of copy cycles. Pawl 230 isspring biased toward the teeth of ratchet 228, but normally is preventedfrom driving engagement therewith by a main counter wheel 232 providedwith a single ratchet tooth 234. When counter wheel 232 is advanced tobring tooth 234 in'alignment with drive pawl 230, the drive pawl isenabled to advance drive ratchet 228 upon the next cycle of the supportdoors. The mechanism is also provided with an adjustable advance cam Iposition as'illustrated in FIG. 11. When the support 11, a secondembodiment of the photoconductor ad- 236 which determines the length ofeach incremental advancement of the photoconductor web. A pin or finger240 is mounted on pawl 230 and rides on a cam surface 238 to preventoperative engagement of the drive pawl with the teeth of ratchet 228through portion of the advance stroke. As pin 240 moves downwardlybeyond the cam surface 238, drive pawl 230 is permitted to operativelyengage the teeth of ratchet 228. That portion of the stroke during whichthe drive pawl is held inoperative may be set by adjusting the angularposition of cam 236 by way of bolt 242 which'cooperates with an arcuateslot 244 in the cam.

Drive pawl 230 is mounted to an advance shaft 246 carried by a pawldrive lever 248. A counter advance pawl 250 is also mounted to shaft 246and is appropriately spring biased toward a counter advance ratchet 252.A drive gear 254 is attached to support door 66 for movement therewithand meshes with a driven gear 256 which is rotatably mounted about driveshaft 220 by way of a bushing 258, as best illustrated in FIG. 12. Drivelever 248 is mounted to bushing 258 and rotates with gear 256. Thus,cycling of the support door causes a corresponding reciprocation oflever '248, which in turn reciprocates pawls 230 and 250 along apredetermined arcuate path. 7

. The gearing is such that when support door 66 is in itsnormal outerposition, drive lever 248 is in its lower doors-are pivoted inward,drive lever 248 is pivoted in a counterclockwise direction to a positionshown in dash line at 248a in FIG. 10. As the support doors moveoutwardly, pawls 230 and 250-are moved downward. Each downward stroke ofthe counter pawl 250 is effective to advance counter ratchet 252 apreselected number of teeth. A counter rate cam 259, similar to cam 236,engages a pin 260 of pawl 250 to prevent pawl s engagement with ratchet252 during a portion of each stroke. The angular position of cam 258 maybe adjusted by way of bolt 242. A pair of one-way pawls 2'62 and 264 areprovidedfor preventing ratchets 228 and 252 from creeping backward in acounterclockwise direction. Main counter wheel 232 is affixed to counterratchet wheel 252 for rotation therewith, such that each advancement .ofthe counter ratchet moves ratchet tooth 234 closer to drive pawl 230.After a preselected number of counts or advancement of the counterratchet, ratchet tooth 234 falls within the stroke area of tripawl 230,enabling the drive pawl on the next stroke.

When each incremental advancement is effected through mechanism 218, itis essential that the slack portion of photoconductor be wound ontotake-up spool 226. This is achieved by way of tensioning lever 266including a slot 268 which receives an extension of shaft 246 carried bydrive lever 248. This mechanical arrangement is best illustrated inFIGS. wand 12. The tensioning lever isprovided with a drive surface 270which frictionally engages a corresponding surface 272 associated withtake-up spool 226. The opposite end of the take-up spool is mounted to aone-way bearing 274 which permits rotation of the take-upspool is acounterclockwise direction only. Thus, as tensioning lever 266 isreciprocated, take-up spool 226 is rotated in a counterclockwisedirection until the web is snugly wound and held in tension between thetake-up spool and controller rollers 222 and 224. Subsequentreciprocation of the tensioning lever is accompanied by slippage atfrictional surfaces 270 and 272. This slippage also occurs when thetensioning lever is pivoted in a clockwise direction due to the one-waybearing 274.

The second embodiment of the advance mechanism further differs from thefirst embodiment in that-the imaging portion of the web is maintained intension during exposure by a tensioning mechanism associated with thesupply spool, rather than the take-up spool. The supply spool, indicatedat 276, includes a notched disc 276 drivingly connected to a tensioningmechanism 280 by way of a connection pin 282. A housing 284 carries pin282 and is attached to the outer end of a coil spring 286. A supportshaft 290 rotatably supports one end of the take-up spool and isattached to the inner end of coil spring 286. A bushing 288 rotatablysupports housing 284 to shaft 290. A friction clutch, generallyindicated bythe numeral 292, includes a stationary member 294 attachedto the frame structures and plate 70. A. moveable member 296 is keyed toshaft 290 and' frictionally engages stationary member 294 along the areaindicated at 298.

When the photoconductor is incrementally advanced,supply spool 276 isrotated in a counterclockwise direction, which in turn winds spring 286by way of housing 284 and pin 282. If thespring is fully wound, shaft290 is free to rotate through slip clutch 292.-After the incrementaladvance is completed, spring 286is left in a fully wound condition..Whenthe support doors swing inward for the next exposure, the excessphotoconductor is pulled in by clockwise rotation of take-up spool 276under the influence of coil spring 286.

From the foregoing description, it will be appreciated that the secondembodiment of the advance mechanism provides automatic incrementaladvance of the photoconductor web after a preselected number of copycycles. By adjusting the position of cam 258, the number of copy cyclesrequired before advancement may be conveniently selected. In addition,the length of incremental advancement may be adjusted by way of cam 236.Cycling of the support door advances the counter mechanism and effectsadvancement of the photoconductor upon reaching the preselected count.It will also be appreciated that cycling of the support doors maintainsthe photoconductor snugly wound on the take-up spool by way oftensioning lever 266, while the imaging portion of the web isautomatically held in tension by way of the tensioning mechanismassociated with the supply spool.

it is not intended that the second embodiment of the advance mechanismbe limited to the mechanical counter illustrated in the drawings asother types of counters may be utilized, if practical to do so.Furthermore, the counting mechanism maybe eliminated in j lieu of veryfineincremental advance which every copy cycle. I

While the invention has been described with reference to the structuredisclosed herein, it is not intended that the present invention beconfined tothe details set forth, and this application is intended tocover modifications or changes as may come within the scope of thefollowing claims.

' I claim: I

l. A photoconductor-carrying assembly for use with an'electrophotographic reproduction apparatus, said assembly comprising:

a frame structure'including a normally curved support surface, means forrotating said frame structure about an axis,

2. The'assembly set forth claim 1 together with means for holding saidportion of said flexible photoconductor element in tension to maintainsaid photoconductor element in said planar configuration when saidsupport surface is moved inwardly. v Y

3. The assembly set forth in claim 2 wherein said support surfaceis'normally of part cylindrical configuration.

4. The assembly set forth in claim 1 wherein said support surface isdefined by at least one.pi votally mounted support member operativelyconnectedto said movement means for pivotal movement thereby between anormal position and a folded position.

5. The assembly set forth in claim 4 wherein said movement meansincludes actuation means operatively connected to said support memberforeffectingitspivotal inward movement to said folded position .inresponse to rotation of said frame structure to a first predeterminedangular position.

6. The assembly set forth in claim 5 wherein said actuation means alsoeffects return of said support member to said normal position inresponse to rotation of said frame structure to a second predeterminedangular position. i I

7. The assembly setforth in claim 6 wherein said actuation meansincludes a stationary cam member mounted adjacent said frame structureanda cam follower carried by said support member operativelyengageableby said cam member.

8. The assembly set forth in claim 1 wherein said support surface isdefined by a pair of normally mated pivotally mounted support memberseach operatively connected to said movement means for pivotal movementthereby between a normal position and a folded position.

9. The assembly set forth inclaim 8 wherein said movement means includesactuation means operatively connected to said pair of support membersfor pivotally effecting their inward movement to said folded posioccurson- 19. The assembly set forth in claim 18 wherein the length of saidintermediateportion of the photocon- 10. The assembly as set forth inclaim 9 wherein said configuration when said support membersare in saidfoldedpositions.

13. The assembly as set forth in claim 12 wherein said tensioning meansis yieldable to allow the length of said portion of photoconductorelement between said first and second points to vary under to influenceof said support members.

14. A photoconductor-carrying assembly for use with anelectrophotographic reproduction apparatus, said assembly comprising: i

a frame structure including a support member defining a normally curvedsupport surface,

motive means for rotating said frame structure about an axis,

a flexible photoconductor element comprising a web,

with an intermediate portion extending between first and second spacedpoints associated with said frame structure and normally engagingsaidcurved 'support surface to assume the configuration thereof,

supplymeans associated with said frame structure for storing a supplyportion of said photoconductor web,

take-up means associated with said frame structure for advancing saidweb and storing a used portion thereof, said intermediate portion beingbetween said supply portion and saidused portion of photoconductor weband defining at least one image area,-and

means associated with said frame structure for cyclicly substantiallydisengaging said intermediate portion of the photoconductor web fromsaid support surface and allowing said intermediate portion of saidframe structure to assume a substantially planar configuration andsubsequently re-engaging said intermediate portion with said supportsurface;

15. The assembly set forth in claim 14 wherein said supply means andsaid take-up means are carried by said frame structure.

16. Theassembly as set forth in claim 15 wherein said supply means andsaidtake-up means include supply and take-up roller respectively mountedto said frame structure.

17. The assembly set forth in claim 16 together with means for applyingtension to said intermediate portion of said photoconductor element whenin said substantially planar configuration.

18. The assembly-set forth in claim 17 wherein said tensioning means isoperatively connected to at least one of said rollers. a

ductor web between said first and second points when in said curvedconfiguration is greater than when in said substantially planarconfiguration, said tensioning means including means for preventingslack in said photoconductor web between said first and second pointswhen the configuration of the intermediate portion of the web ischangedfrom curved to substantially planar by said disengagement means.

20. The assembly as set forth in claim 14 wherein said take-up means isoperatively connected to said cyclic disengagement means for operationthereby.

21. Theassembly as set forth in claim 14 wherein each actuation of saidtake-up means incrementally ad,- vances said web anamount less than oneof said image areas. I

22. The assembly as set forth in claim 21 wherein take-up means isactuated in response .to completion of a predetermined number ofoperations of said cyclic disengagement means.

23. The assembly as set forth in claim 20 wherein said take-up meansinclude means for effectively counting the number of cyclesof saiddisengagement means to effect said selective advancement of said webupon reaching a predetermined count. 7

24. The assembly as set forth in claim 14 wherein said disengagementmeans is operatively connected to said support member to effect movementthereof from its normal position in one direction to substantiallydisengage said intermediate'portion of photoconductor from said supportsurface to assume said planar configuration and subsequenti ally effectmovement of said support member in the opposite direction for return toits normal position. v g

25. The assembly as set forth in claim 24 wherein'said support member ispivotally mounted to said frame structure and moved pivotally by saiddisengagement means.

26. The assembly as set forth in claim 25 wherein said take-up meansincludes a take-up roller in operative engagement with said web, a maindrive ratchet drivingly connected to said take-up roller and a drivepawl operatively connected to said support member for movement thereby,said counting means preventing driving engagement of said drive pawlwith said drive ratchet until said predetermined count is reached.

27. A photoconductor-carrying assembly for use with anelectrophotographic reproduction apparatus, said assembly comprising:

a stationary housing, a frame structure rotatably mounted to saidhousing, said frame structure including a support surface,

motive means operatively connected to said frame structure for.effecting rotation thereof about an axis relative to said housing,

an elongated photoconductor element carried by said frame structure andextending between a supply location and a take-up location with anintermediate portion normally engaging said support surface,

advance means operatively connected to said photoconductor element foradvancing said photoconductor element over said support surface towardsaid take-up location from said supply location, said advance meansincluding a rotatable drive element carried by said frame structure,said drive element moving in a circular path about said axis of rotationwhen said frame structure is rotated by said motive means, and 1actuation means associated with said stationary housing and selectivelymovable between a normal retracted position and an advance position,said actuation means when in said advanceposition operatively engagingsaid drive element to effect rotation thereof to operate said advancemeans.

28. The assembly set forth in claim 27 wherein said actuation meansincludes a generally arcuate actuation member supported by saidstationaryhousing, said actuation member intersecting said circular pathwhen in said advanced position toengage drive element and effectrotation thereof due to rotation of said frame structure.

29. The assembly set forth in claim 28 wherein said drive elementincludes a gear teeth; said actuation member comprising a curved rack:for operative engagement with said gear teeth when said rack is in saidadvance position.

30. The assembly set forth in claim 28 wherein said actuation meansincludes electromechanical means responsive to a photoconductor advancesignal to move said actuation member to said advance position.

31. The assembly set forth in claim 30 wherein said drive elementincludes gear teeth, said actuation member comprising a curved rack foroperative engagement with said gear teeth when said rack is in saidadvance position.

32. The assembly set forth in claim 31 wherein said advance meansincludes means for maintaining said intermediate portion of saidphotoconductor element in tension.

1. A photoconductor-carrying assembly for use with an electrophotographic reproduction apparatus, said assembly comprising: a frame structure including a normally curved support surface, means for rotating said frame structure about an axis, a flexible photoconductor element carried by said frame structure, a portion of said photoconductor element extending between first and second points of said frame structure and normally engaging said curved support surface to assume the configuration thereof, and means for selectively moving at least a portion of said support surface inwardly toward said axis of rotation whereby said portion of said flexible photoconductor element assumes a generally planar configuration to Define an imaging plane for exposure.
 2. The assembly set forth in claim 1 together with means for holding said portion of said flexible photoconductor element in tension to maintain said photoconductor element in said planar configuration when said support surface is moved inwardly.
 3. The assembly set forth in claim 2 wherein said support surface is normally of part cylindrical configuration.
 4. The assembly set forth in claim 1 wherein said support surface is defined by at least one pivotally mounted support member operatively connected to said movement means for pivotal movement thereby between a normal position and a folded position.
 5. The assembly set forth in claim 4 wherein said movement means includes actuation means operatively connected to said support member for effecting its pivotal inward movement to said folded position in response to rotation of said frame structure to a first predetermined angular position.
 6. The assembly set forth in claim 5 wherein said actuation means also effects return of said support member to said normal position in response to rotation of said frame structure to a second predetermined angular position.
 7. The assembly set forth in claim 6 wherein said actuation means includes a stationary cam member mounted adjacent said frame structure and a cam follower carried by said support member operatively engageable by said cam member.
 8. The assembly set forth in claim 1 wherein said support surface is defined by a pair of normally mated pivotally mounted support members each operatively connected to said movement means for pivotal movement thereby between a normal position and a folded position.
 9. The assembly set forth in claim 8 wherein said movement means includes actuation means operatively connected to said pair of support members for pivotally effecting their inward movement to said folded positions in response to rotation of said frame structure to a first predetermined angular position.
 10. The assembly as set forth in claim 9 wherein said actuation means also effects return of said support members to their respective normal positions when said frame structure is rotated to a second predetermined angular position.
 11. The assembly as set forth in claim 10 wherein said actuation means includes a pair of cam members mounted adjacent said frame structure and a cam follower carried by each of said support members operatively engageable by said cam member.
 12. The assembly as set forth in claim 11 together with means for holding said portion of said flexible photoconductor element in tension to maintain said planar configuration when said support members are in said folded positions.
 13. The assembly as set forth in claim 12 wherein said tensioning means is yieldable to allow the length of said portion of photoconductor element between said first and second points to vary under to influence of said support members.
 14. A photoconductor-carrying assembly for use with an electrophotographic reproduction apparatus, said assembly comprising: a frame structure including a support member defining a normally curved support surface, motive means for rotating said frame structure about an axis, a flexible photoconductor element comprising a web, with an intermediate portion extending between first and second spaced points associated with said frame structure and normally engaging said curved support surface to assume the configuration thereof, supply means associated with said frame structure for storing a supply portion of said photoconductor web, take-up means associated with said frame structure for advancing said web and storing a used portion thereof, said intermediate portion being between said supply portion and said used portion of photoconductor web and defining at least one image area, and means associated with said frame structure for cyclicly substantially disengaging said intermediate portion of the photoconductor web from said support surface and allowing said Intermediate portion of said frame structure to assume a substantially planar configuration and subsequently re-engaging said intermediate portion with said support surface.
 15. The assembly set forth in claim 14 wherein said supply means and said take-up means are carried by said frame structure.
 16. The assembly as set forth in claim 15 wherein said supply means and said take-up means include supply and take-up roller respectively mounted to said frame structure.
 17. The assembly set forth in claim 16 together with means for applying tension to said intermediate portion of said photoconductor element when in said substantially planar configuration.
 18. The assembly set forth in claim 17 wherein said tensioning means is operatively connected to at least one of said rollers.
 19. The assembly set forth in claim 18 wherein the length of said intermediate portion of the photoconductor web between said first and second points when in said curved configuration is greater than when in said substantially planar configuration, said tensioning means including means for preventing slack in said photoconductor web between said first and second points when the configuration of the intermediate portion of the web is changed from curved to substantially planar by said disengagement means.
 20. The assembly as set forth in claim 14 wherein said take-up means is operatively connected to said cyclic disengagement means for operation thereby.
 21. The assembly as set forth in claim 14 wherein each actuation of said take-up means incrementally advances said web an amount less than one of said image areas.
 22. The assembly as set forth in claim 21 wherein take-up means is actuated in response to completion of a predetermined number of operations of said cyclic disengagement means.
 23. The assembly as set forth in claim 20 wherein said take-up means include means for effectively counting the number of cycles of said disengagement means to effect said selective advancement of said web upon reaching a predetermined count.
 24. The assembly as set forth in claim 14 wherein said disengagement means is operatively connected to said support member to effect movement thereof from its normal position in one direction to substantially disengage said intermediate portion of photoconductor from said support surface to assume said planar configuration and subsequentially effect movement of said support member in the opposite direction for return to its normal position.
 25. The assembly as set forth in claim 24 wherein said support member is pivotally mounted to said frame structure and moved pivotally by said disengagement means.
 26. The assembly as set forth in claim 25 wherein said take-up means includes a take-up roller in operative engagement with said web, a main drive ratchet drivingly connected to said take-up roller and a drive pawl operatively connected to said support member for movement thereby, said counting means preventing driving engagement of said drive pawl with said drive ratchet until said predetermined count is reached.
 27. A photoconductor-carrying assembly for use with an electrophotographic reproduction apparatus, said assembly comprising: a stationary housing, a frame structure rotatably mounted to said housing, said frame structure including a support surface, motive means operatively connected to said frame structure for effecting rotation thereof about an axis relative to said housing, an elongated photoconductor element carried by said frame structure and extending between a supply location and a take-up location with an intermediate portion normally engaging said support surface, advance means operatively connected to said photoconductor element for advancing said photoconductor element over said support surface toward said take-up location from said supply location, said advance means including a rotatable drive element carried by said frame structure, said drive element moving in a circular path about said axis of rotation When said frame structure is rotated by said motive means, and actuation means associated with said stationary housing and selectively movable between a normal retracted position and an advance position, said actuation means when in said advance position operatively engaging said drive element to effect rotation thereof to operate said advance means.
 28. The assembly set forth in claim 27 wherein said actuation means includes a generally arcuate actuation member supported by said stationary housing, said actuation member intersecting said circular path when in said advanced position to engage drive element and effect rotation thereof due to rotation of said frame structure.
 29. The assembly set forth in claim 28 wherein said drive element includes a gear teeth, said actuation member comprising a curved rack for operative engagement with said gear teeth when said rack is in said advance position.
 30. The assembly set forth in claim 28 wherein said actuation means includes electromechanical means responsive to a photoconductor advance signal to move said actuation member to said advance position.
 31. The assembly set forth in claim 30 wherein said drive element includes gear teeth, said actuation member comprising a curved rack for operative engagement with said gear teeth when said rack is in said advance position.
 32. The assembly set forth in claim 31 wherein said advance means includes means for maintaining said intermediate portion of said photoconductor element in tension. 